Sorry if this comes across as overly facetious — I’m sure you have a reason for doing it that way! — but would it not be easier just to bow to convention and rename your .js files to .jsx?
Probably. It's just that I've always used .js for my projects (decades). Such a rename would likely result in configuration changes to the other tools I use, but indeed they are better documented. When faced with a multiplicity of conventions I pick one and stick to it; the tools are flexible enough to work with it I'm sure, the real issue is of discoverability.
But it’s not just convention… JSX files are not valid JS files. Also, as a programmer, I would be annoyed to open a JS file and find out it’s actually something else.